The message of TWCSR is explained in the poem that the house reads at the end. Basically, it says that if/when the human race dies, the trees will keep growing, the bird will keep singing, and life will go on without us.
If something bad happens to you, life will go on and you should not worry about the small things.

The house doesn't care that there aren't people living in it anymore. It keeps going about it's daily routine because that's how it was programmed to run. Even after the fire, the one wall of the house that is still standing keeps repeating the date on the next day.